1 /*
2 * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/classLoaderData.inline.hpp"
27 #include "classfile/loaderConstraints.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "runtime/handles.inline.hpp"
31 #include "runtime/safepoint.hpp"
32 #include "utilities/hashtable.inline.hpp"
33
34 void LoaderConstraintEntry::set_loader(int i, oop p) {
35 set_loader_data(i, ClassLoaderData::class_loader_data(p));
36 }
37
38 LoaderConstraintTable::LoaderConstraintTable(int nof_buckets)
39 : Hashtable<InstanceKlass*, mtClass>(nof_buckets, sizeof(LoaderConstraintEntry)) {};
40
41
42 LoaderConstraintEntry* LoaderConstraintTable::new_entry(
43 unsigned int hash, Symbol* name,
44 InstanceKlass* klass, int num_loaders,
45 int max_loaders) {
46 LoaderConstraintEntry* entry;
47 entry = (LoaderConstraintEntry*)Hashtable<InstanceKlass*, mtClass>::new_entry(hash, klass);
48 entry->set_name(name);
49 entry->set_num_loaders(num_loaders);
50 entry->set_max_loaders(max_loaders);
51 return entry;
52 }
53
54 void LoaderConstraintTable::free_entry(LoaderConstraintEntry *entry) {
55 // decrement name refcount before freeing
56 entry->name()->decrement_refcount();
57 Hashtable<InstanceKlass*, mtClass>::free_entry(entry);
58 }
59
60 // Enhanced Class Redefinition support
61 void LoaderConstraintTable::classes_do(KlassClosure* f) {
62 for (int index = 0; index < table_size(); index++) {
63 for (LoaderConstraintEntry* probe = bucket(index);
64 probe != NULL;
65 probe = probe->next()) {
66 if (probe->klass() != NULL) {
67 f->do_klass(probe->klass());
68 }
69 }
70 }
71 }
72
73 // The loaderConstraintTable must always be accessed with the
74 // SystemDictionary lock held. This is true even for readers as
75 // entries in the table could be being dynamically resized.
76
77 LoaderConstraintEntry** LoaderConstraintTable::find_loader_constraint(
78 Symbol* name, Handle loader) {
79
80 unsigned int hash = compute_hash(name);
81 int index = hash_to_index(hash);
82 LoaderConstraintEntry** pp = bucket_addr(index);
83 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(loader());
84
85 while (*pp) {
86 LoaderConstraintEntry* p = *pp;
87 if (p->hash() == hash) {
88 if (p->name() == name) {
89 for (int i = p->num_loaders() - 1; i >= 0; i--) {
90 if (p->loader_data(i) == loader_data) {
91 return pp;
92 }
93 }
94 }
95 }
96 pp = p->next_addr();
97 }
98 return pp;
99 }
100
101
102 void LoaderConstraintTable::purge_loader_constraints() {
103 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
104 // Remove unloaded entries from constraint table
105 for (int index = 0; index < table_size(); index++) {
106 LoaderConstraintEntry** p = bucket_addr(index);
107 while(*p) {
108 LoaderConstraintEntry* probe = *p;
109 InstanceKlass* klass = probe->klass();
110 // Remove klass that is no longer alive
111 if (klass != NULL &&
112 klass->class_loader_data()->is_unloading()) {
113 probe->set_klass(NULL);
114 if (log_is_enabled(Info, class, loader, constraints)) {
115 ResourceMark rm;
116 outputStream* out = Log(class, loader, constraints)::info_stream();
117 out->print_cr("purging class object from constraint for name %s,"
118 " loader list:",
119 probe->name()->as_C_string());
120 for (int i = 0; i < probe->num_loaders(); i++) {
121 out->print_cr(" [%d]: %s", i,
122 probe->loader_data(i)->loader_name());
123 }
124 }
125 }
126 // Remove entries no longer alive from loader array
127 int n = 0;
128 while (n < probe->num_loaders()) {
129 if (probe->loader_data(n)->is_unloading()) {
130 if (log_is_enabled(Info, class, loader, constraints)) {
131 ResourceMark rm;
132 outputStream* out = Log(class, loader, constraints)::info_stream();
133 out->print_cr("purging loader %s from constraint for name %s",
134 probe->loader_data(n)->loader_name(),
135 probe->name()->as_C_string()
136 );
137 }
138
139 // Compact array
140 int num = probe->num_loaders() - 1;
141 probe->set_num_loaders(num);
142 probe->set_loader_data(n, probe->loader_data(num));
143 probe->set_loader_data(num, NULL);
144
145 if (log_is_enabled(Info, class, loader, constraints)) {
146 ResourceMark rm;
147 outputStream* out = Log(class, loader, constraints)::info_stream();
148 out->print_cr("new loader list:");
149 for (int i = 0; i < probe->num_loaders(); i++) {
150 out->print_cr(" [%d]: %s", i,
151 probe->loader_data(i)->loader_name());
152 }
153 }
154
155 continue; // current element replaced, so restart without
156 // incrementing n
157 }
158 n++;
159 }
160 // Check whether entry should be purged
161 if (probe->num_loaders() < 2) {
162 if (log_is_enabled(Info, class, loader, constraints)) {
163 ResourceMark rm;
164 outputStream* out = Log(class, loader, constraints)::info_stream();
165 out->print_cr("purging complete constraint for name %s",
166 probe->name()->as_C_string());
167 }
168
169 // Purge entry
170 *p = probe->next();
171 FREE_C_HEAP_ARRAY(oop, probe->loaders());
172 free_entry(probe);
173 } else {
174 #ifdef ASSERT
175 if (probe->klass() != NULL) {
176 ClassLoaderData* loader_data =
177 probe->klass()->class_loader_data();
178 assert(!loader_data->is_unloading(), "klass should be live");
179 }
180 #endif
181 // Go to next entry
182 p = probe->next_addr();
183 }
184 }
185 }
186 }
187
188 bool LoaderConstraintTable::add_entry(Symbol* class_name,
189 InstanceKlass* klass1, Handle class_loader1,
190 InstanceKlass* klass2, Handle class_loader2) {
191 int failure_code = 0; // encode different reasons for failing
192
193 if (klass1 != NULL && klass2 != NULL && klass1 != klass2) {
194 failure_code = 1;
195 } else {
196 InstanceKlass* klass = klass1 != NULL ? klass1 : klass2;
197
198 LoaderConstraintEntry** pp1 = find_loader_constraint(class_name,
199 class_loader1);
200 if (*pp1 != NULL && (*pp1)->klass() != NULL) {
201 if (klass != NULL) {
202 if (klass != (*pp1)->klass()) {
203 failure_code = 2;
204 }
205 } else {
206 klass = (*pp1)->klass();
207 }
208 }
209
210 LoaderConstraintEntry** pp2 = find_loader_constraint(class_name,
211 class_loader2);
212 if (*pp2 != NULL && (*pp2)->klass() != NULL) {
213 if (klass != NULL) {
214 if (klass != (*pp2)->klass()) {
215 failure_code = 3;
216 }
217 } else {
218 klass = (*pp2)->klass();
219 }
220 }
221
222 if (failure_code == 0) {
223 if (*pp1 == NULL && *pp2 == NULL) {
224 unsigned int hash = compute_hash(class_name);
225 int index = hash_to_index(hash);
226 LoaderConstraintEntry* p;
227 p = new_entry(hash, class_name, klass, 2, 2);
228 p->set_loaders(NEW_C_HEAP_ARRAY(ClassLoaderData*, 2, mtClass));
229 p->set_loader(0, class_loader1());
230 p->set_loader(1, class_loader2());
231 p->set_klass(klass);
232 p->set_next(bucket(index));
233 set_entry(index, p);
234 if (log_is_enabled(Info, class, loader, constraints)) {
235 ResourceMark rm;
236 outputStream* out = Log(class, loader, constraints)::info_stream();
237 out->print_cr("adding new constraint for name: %s, loader[0]: %s,"
238 " loader[1]: %s",
239 class_name->as_C_string(),
240 SystemDictionary::loader_name(class_loader1()),
241 SystemDictionary::loader_name(class_loader2())
242 );
243 }
244 } else if (*pp1 == *pp2) {
245 /* constraint already imposed */
246 if ((*pp1)->klass() == NULL) {
247 (*pp1)->set_klass(klass);
248 if (log_is_enabled(Info, class, loader, constraints)) {
249 ResourceMark rm;
250 outputStream* out = Log(class, loader, constraints)::info_stream();
251 out->print_cr("setting class object in existing constraint for"
252 " name: %s and loader %s",
253 class_name->as_C_string(),
254 SystemDictionary::loader_name(class_loader1())
255 );
256 }
257 } else {
258 assert((*pp1)->klass() == klass, "loader constraints corrupted");
259 }
260 } else if (*pp1 == NULL) {
261 extend_loader_constraint(*pp2, class_loader1, klass);
262 } else if (*pp2 == NULL) {
263 extend_loader_constraint(*pp1, class_loader2, klass);
264 } else {
265 merge_loader_constraints(pp1, pp2, klass);
266 }
267 }
268 }
269
270 if (failure_code != 0 && log_is_enabled(Info, class, loader, constraints)) {
271 ResourceMark rm;
272 outputStream* out = Log(class, loader, constraints)::info_stream();
273 const char* reason = "";
274 switch(failure_code) {
275 case 1: reason = "the class objects presented by loader[0] and loader[1]"
276 " are different"; break;
277 case 2: reason = "the class object presented by loader[0] does not match"
278 " the stored class object in the constraint"; break;
279 case 3: reason = "the class object presented by loader[1] does not match"
280 " the stored class object in the constraint"; break;
281 default: reason = "unknown reason code";
282 }
283 out->print_cr("failed to add constraint for name: %s, loader[0]: %s,"
284 " loader[1]: %s, Reason: %s",
285 class_name->as_C_string(),
286 SystemDictionary::loader_name(class_loader1()),
287 SystemDictionary::loader_name(class_loader2()),
288 reason
289 );
290 }
291
292 return failure_code == 0;
293 }
294
295
296 // return true if the constraint was updated, false if the constraint is
297 // violated
298 bool LoaderConstraintTable::check_or_update(InstanceKlass* k,
299 Handle loader,
300 Symbol* name) {
301 LoaderConstraintEntry* p = *(find_loader_constraint(name, loader));
302 if (p && p->klass() != NULL && p->klass() != k) {
303 if (log_is_enabled(Info, class, loader, constraints)) {
304 ResourceMark rm;
305 outputStream* out = Log(class, loader, constraints)::info_stream();
306 out->print_cr("constraint check failed for name %s, loader %s: "
307 "the presented class object differs from that stored",
308 name->as_C_string(),
309 SystemDictionary::loader_name(loader()));
310 }
311 return false;
312 } else {
313 if (p && p->klass() == NULL) {
314 p->set_klass(k);
315 if (log_is_enabled(Info, class, loader, constraints)) {
316 ResourceMark rm;
317 outputStream* out = Log(class, loader, constraints)::info_stream();
318 out->print_cr("updating constraint for name %s, loader %s, "
319 "by setting class object",
320 name->as_C_string(),
321 SystemDictionary::loader_name(loader()));
322 }
323 }
324 return true;
325 }
326 }
327
328 InstanceKlass* LoaderConstraintTable::find_constrained_klass(Symbol* name,
329 Handle loader) {
330 LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));
331 if (p != NULL && p->klass() != NULL) {
332 assert(p->klass()->is_instance_klass(), "sanity");
333 if (p->klass()->is_loaded()) {
334 // Only return fully loaded classes. Classes found through the
335 // constraints might still be in the process of loading.
336 return NULL;
337 }
338 return p->klass();
339 }
340
341 // No constraints, or else no klass loaded yet.
342 return NULL;
343 }
344
345 void LoaderConstraintTable::ensure_loader_constraint_capacity(
346 LoaderConstraintEntry *p,
347 int nfree) {
348 if (p->max_loaders() - p->num_loaders() < nfree) {
349 int n = nfree + p->num_loaders();
350 ClassLoaderData** new_loaders = NEW_C_HEAP_ARRAY(ClassLoaderData*, n, mtClass);
351 memcpy(new_loaders, p->loaders(), sizeof(ClassLoaderData*) * p->num_loaders());
352 p->set_max_loaders(n);
353 FREE_C_HEAP_ARRAY(ClassLoaderData*, p->loaders());
354 p->set_loaders(new_loaders);
355 }
356 }
357
358
359 void LoaderConstraintTable::extend_loader_constraint(LoaderConstraintEntry* p,
360 Handle loader,
361 InstanceKlass* klass) {
362 ensure_loader_constraint_capacity(p, 1);
363 int num = p->num_loaders();
364 p->set_loader(num, loader());
365 p->set_num_loaders(num + 1);
366 if (log_is_enabled(Info, class, loader, constraints)) {
367 ResourceMark rm;
368 outputStream* out = Log(class, loader, constraints)::info_stream();
369 out->print_cr("extending constraint for name %s by adding loader[%d]: %s %s",
370 p->name()->as_C_string(),
371 num,
372 SystemDictionary::loader_name(loader()),
373 (p->klass() == NULL ? " and setting class object" : "")
374 );
375 }
376 if (p->klass() == NULL) {
377 p->set_klass(klass);
378 } else {
379 assert(klass == NULL || p->klass() == klass, "constraints corrupted");
380 }
381 }
382
383
384 void LoaderConstraintTable::merge_loader_constraints(
385 LoaderConstraintEntry** pp1,
386 LoaderConstraintEntry** pp2,
387 InstanceKlass* klass) {
388 // make sure *pp1 has higher capacity
389 if ((*pp1)->max_loaders() < (*pp2)->max_loaders()) {
390 LoaderConstraintEntry** tmp = pp2;
391 pp2 = pp1;
392 pp1 = tmp;
393 }
394
395 LoaderConstraintEntry* p1 = *pp1;
396 LoaderConstraintEntry* p2 = *pp2;
397
398 ensure_loader_constraint_capacity(p1, p2->num_loaders());
399
400 for (int i = 0; i < p2->num_loaders(); i++) {
401 int num = p1->num_loaders();
402 p1->set_loader_data(num, p2->loader_data(i));
403 p1->set_num_loaders(num + 1);
404 }
405
406 if (log_is_enabled(Info, class, loader, constraints)) {
407 ResourceMark rm;
408 outputStream* out = Log(class, loader, constraints)::info_stream();
409 out->print_cr("merged constraints for name %s, new loader list:",
410 p1->name()->as_C_string()
411 );
412
413 for (int i = 0; i < p1->num_loaders(); i++) {
414 out->print_cr(" [%d]: %s", i,
415 p1->loader_data(i)->loader_name());
416 }
417 if (p1->klass() == NULL) {
418 out->print_cr("... and setting class object");
419 }
420 }
421
422 // p1->klass() will hold NULL if klass, p2->klass(), and old
423 // p1->klass() are all NULL. In addition, all three must have
424 // matching non-NULL values, otherwise either the constraints would
425 // have been violated, or the constraints had been corrupted (and an
426 // assertion would fail).
427 if (p2->klass() != NULL) {
428 assert(p2->klass() == klass, "constraints corrupted");
429 }
430 if (p1->klass() == NULL) {
431 p1->set_klass(klass);
432 } else {
433 assert(p1->klass() == klass, "constraints corrupted");
434 }
435
436 *pp2 = p2->next();
437 FREE_C_HEAP_ARRAY(oop, p2->loaders());
438 free_entry(p2);
439 return;
440 }
441
442
443 void LoaderConstraintTable::verify(Dictionary* dictionary,
444 PlaceholderTable* placeholders) {
445 Thread *thread = Thread::current();
446 for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {
447 for (LoaderConstraintEntry* probe = bucket(cindex);
448 probe != NULL;
449 probe = probe->next()) {
450 if (probe->klass() != NULL) {
451 InstanceKlass* ik = probe->klass();
452 guarantee(ik->name() == probe->name(), "name should match");
453 Symbol* name = ik->name();
454 ClassLoaderData* loader_data = ik->class_loader_data();
455 unsigned int d_hash = dictionary->compute_hash(name, loader_data);
456 int d_index = dictionary->hash_to_index(d_hash);
457 InstanceKlass* k = dictionary->find_class(d_index, d_hash, name, loader_data);
458 if (k != NULL) {
459 // We found the class in the system dictionary, so we should
460 // make sure that the Klass* matches what we already have.
461 guarantee(k == probe->klass(), "klass should be in dictionary");
462 } else {
463 // If we don't find the class in the system dictionary, it
464 // has to be in the placeholders table.
465 unsigned int p_hash = placeholders->compute_hash(name, loader_data);
466 int p_index = placeholders->hash_to_index(p_hash);
467 PlaceholderEntry* entry = placeholders->get_entry(p_index, p_hash,
468 name, loader_data);
469
470 // The InstanceKlass might not be on the entry, so the only
471 // thing we can check here is whether we were successful in
472 // finding the class in the placeholders table.
473 guarantee(entry != NULL, "klass should be in the placeholders");
474 }
475 }
476 for (int n = 0; n< probe->num_loaders(); n++) {
477 assert(ClassLoaderDataGraph::contains_loader_data(probe->loader_data(n)), "The loader is missing");
478 }
479 }
480 }
481 }
482
483 #ifndef PRODUCT
484
485 // Called with the system dictionary lock held
486 void LoaderConstraintTable::print() {
487 ResourceMark rm;
488 assert_locked_or_safepoint(SystemDictionary_lock);
489 tty->print_cr("Java loader constraints (entries=%d)", _loader_constraint_size);
490 for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {
491 for (LoaderConstraintEntry* probe = bucket(cindex);
492 probe != NULL;
493 probe = probe->next()) {
494 tty->print("%4d: ", cindex);
495 probe->name()->print();
496 tty->print(" , loaders:");
497 for (int n = 0; n < probe->num_loaders(); n++) {
498 probe->loader_data(n)->print_value();
499 tty->print(", ");
500 }
501 tty->cr();
502 }
503 }
504 }
505 #endif